We (Cloudstitch, YC S15) are building remote work into our company DNA right from the start. It's been an educational journey, and we're stronger team because of it.
One thing we've learned is that "diversity" is so much more than just race/gender/ethnicity. Geographic location, even within the US, can be a profound contributor to the diversity of ideas, experiences, and opportunities. Makes you realize a non-remote team is living in a [geographic] bubble by definition.
If you're interested in building a better web stack / CMS that integrates with your office suite, give us a holler at hello@cloudstitch.com :-)
PS: Re open office plans in early-stage startups, I suspect cost savings are a driving factor.